1. Technical Field
The present invention relates to a method of handling a control rod and a control rod handling apparatus and more particularly to a method of handling a control rod and a control rod handling apparatus which are suited to apply to a boiling water reactor (hereinafter, referred to as BWR).
2. Background Art
To connect a control rod and a control rod drive mechanism (hereinafter, referred to as CRD) that are used in the BWR, a bayonet coupling is used. The control rod connected to the CRD by the bayonet coupling, when the neutron absorption capacity is reduced, is removed from the CRD and is taken out from a reactor pressure vessel. A new control rod is connected to the CRD in place of the taken-out control rod. Such an exchange operation of the control rod, for example, is explained in Japanese Patent 3119728.
The bayonet coupling for the control rod and CRD is described in Japanese Patent 3119728. The bayonet coupling is composed of a coupling socket installed at a lower end portion of the control rod and a coupling spud installed on an upper end portion of the CRD. In the neighborhood of the leading edge of the coupling spud, coupling spud convexities are arranged at intervals of 90° in a peripheral direction and on an inner surface of a hole portion of the coupling socket into which the coupling spud is inserted, joint convexities are arranged at intervals of 90° in the peripheral direction. And, the coupling spud convexities and joint convexities are joined to each other, thus the control rod and CRD are connected to each other. If the coupling socket is rotated at 45° in the peripheral direction, the joint of the coupling spud convexities and joint convexities is released, thus the connection of the control rod and CRD is released.
When attaching the control rod to the CRD, in the state that the control rod is grasped by a control rod grasping equipment installed in the control rod handling apparatus which is hung with a wire rope at the leading edge of a connection member of a supplementary hoist of a fuel exchange apparatus, the wire rope is moved down, thus the control rod handling apparatus and control rod are moved down. If the control rod handling apparatus and control rod are moved down, the coupling socket and the coupling spud do not coincide with each other in phase of the spud convexities and the socket concavities, so that the coupling socket of the control rod makes contact with a upper end face of the coupling spud of the CRD and the descent of the control rod handling apparatus and control rod is stopped. When the control rod handling apparatus and control rod are rotated at 45° in the state that the descent is stopped, the coupling socket and the coupling spud coincide with each other in the phase of the spud convexities and the socket concavities. When the coupling socket and the coupling spud coincide with each other in the phase of the spud convexities and the socket concavities, the control rod handling apparatus and control rod are moved down again. After the coupling spud is inserted completely into the coupling socket, the control rod handling apparatus and control rod are rotated again at 45°, thus the connection of the control rod and CRD is completed.
When removing the control rod from the CRD, firstly, the control rod handling apparatus which is hung with a wire rope at the leading edge of the connection member of the supplementary hoist of the fuel exchange apparatus is moved down, and a handle at the upper end portion of the control rod is grasped by the control rod grasping equipment of the control rod handling apparatus, and thereafter, the control rod is lifted up. Furthermore, the hollow piston of the CRD connected to the control rod by the bayonet coupling is lifted up by operating the CRD. The control rod grasped by the control rod grasping equipment is rotated at 45°, thus the coupling socket installed at the lower end portion of the control rod is rotated relative to the coupling spud of the hollow piston. When the coupling spud and the coupling socket coincide with each other in phase of the spud convexities and the socket concavities, the coupling spud is removed from the coupling socket and only the control rod grasped by the control rod grasping equipment enters the pulled-up state. After the coupling spud is rotated at 45°, the control rod is pulled up and the removal operation of the control rod from the CRD is finished.